Orianna DeMasi, 2007 Summer Student Fellow

Western Connecticut State University McGill UniversityB.S. Mathematics (2009)

Advisor: Steve Lentz, Physical Oceanography

Project: Understanding the Tides South of Martha’s Vineyard.

Goals:

Describe observed tidal features on the portion of the New England shelf south of Martha’s Vineyard.

Try and fit a numerical model to predict sea level height and velocity in the region.

Learn about the dominate forces on the tide in this region.

Overview:This
past summer I worked with Steve Lentz in the Physical Oceanography
Department to determine the characteristics of the tides south of
Martha’s Vineyard. We looked at 5 sets of data that were collected over
various time periods by pressure gauges and current meters from 13
moorings. The data includes a mooring on the 7m isobath, which is
farther inshore than any previous tidal study has looked. I analyzed
the data with T_tide in Matlab to extract maximum amplitudes and phases
for the sea level, cross shelf velocity and along shelf velocity. The
amplitudes and phases from the various studies were complied to give a
comprehensive description of the tidal structure on the inner shelf and
tidal variability across the shelf. We also worked on comparing the
tidal observations a simple baroclinic model that assumes an along
shelf pressure gradient. We found this model to be insufficient to
model the complexities of the tides in the area. However the model was
useful for learning about the predominate forces and momentum balances
over this area of the continental shelf. We found a geostropic balance
(Coriolis component and cross shelf pressure gradient dominant) for the
cross shelf structure, minimal vertical transport, and the along shelf
acceleration term to be of little significance. We also estimated
nonlinear acceleration terms and a frictional bottom stress constant
for the area.